:bug: prompt pre fetch and prompt post fetch has not been tested

[julianstephen]

Describe the bug

Prompt pre fetch and prompt post fetch plugins which changes the prompt is not working correctly

Steps To Reproduce

1. Create mcp server with prompt endpoints

    @mcp.prompt("/echo_prompt", name="echo_user_message", description="Formats a message into a standard prompt template.")
    def echo_prompt(message: str) -> list[Message]:

2. Register pre and post hooks in plugin config
3. On prompt pre hook which modifies the prompt, args are not set correctly

Expected Behavior

Work correctly.

Additional Context

No response

[evaline-ju]

@julianstephen Trying to understand the scope here the "Create mcp server with prompt" seems to be for external plugins. For the MVP focus should we scope this to connecting pre and post prompt hooks for prompts/get calls through the ext-proc and the nemo guardrails plugin, calling the nemo checks API? (Not sure the best nemo-checks call for pre-prompt but the whole prompt message can be checked for the post-prompt call)

[julianstephen]

Internal plugin scope is fine.
Should try prompts/get call through ext-proc->plugin(pre/post)->nemocheck server especially with the post internal hook is modifying the prompt.

[evaline-ju]

We're generally not expecting modifications (just checking->block) for MVP scope

[evaline-ju]

instead of just updating I would like to propose we perhaps reframe this from bug->feature as some scope from #35 like
"Handle prompt checking in nemocheck plugin" and specifically we would check both the requests and responses of MCP prompts/get , with corresponding tests at the ext-server function and nemocheck plugin levels?

[julianstephen]

Mcp-gateway does not federate prompts as of now, and clients don’t see the prompt end points of mcp-servers behind the mcp-gateway. Which means, currently any prompt guardrails will not be invoked, because a mcp-client connected to the mcp-gateway simply do not see the prompt end points.

Will discuss with Christina Xu on when to merge the PR or handle this.